It's heart-wrenching to see photos of oiled birds in the wake of a spill, and rehabilitators spend a lot of time cleaning off the oil. But researchers disagree on how well a cleaned bird will do once it's released back into the wild. Some studies have found that cleaned birds don't breed as well and seem to die quickly.

Brian Sharp, an ornithologist who has a private consulting firm in Oregon, says that on the news lately, he has heard wildlife experts in Louisiana talk about their efforts to clean up wild birds that have gotten covered in oil.

"And they're saying, 'Yes, we can save these birds,' and, 'Yeah, we can take care of them,' " Sharp says.

But he seriously doubts it.

Sharp says he believes many of the cleaned birds will simply not survive after being released back to the wild. That's because in the wake of the Exxon Valdez accident, he looked at several species of seabirds affected by oil to see how long they lived after being washed and banded with ID tags.

Based on tags that were later found, Sharp says the majority of rehabilitated birds didn't last long after being released -- just days, or weeks.

The birds hadn't been just covered in oil -- they'd ingested it as they tried to preen. Sharp says he does understand how agonizing it is to see the suffering of oiled birds, and he thinks that if people want to try to clean them, that's their choice.

"Just so that they don't deceive themselves and the public that they're really having great, grand results and saving lots and lots, a high proportion of the birds," Sharp says. "Because it's just the opposite."

Other scientists have come to a similar conclusion. One biologist in Germany recently has been widely quoted as saying that oiled birds should be left alone or euthanized.

Rehabilitation

That bothers Michael Fry, a toxicologist who works at the American Bird Conservancy. Some research doesn't support such a grim view, he says.

"The success at rehabilitation goes all over the map, from like 3 percent of the birds that are brought in, to over 90 percent of the birds that are brought in," Fry says.

Many factors can influence the outcome of a rehabilitation effort, Fry says -- everything from the type of oil to the species of bird.

"Loons and grebes, for instance, are very delicate birds when it comes to oil spills," he says. "Gulls are tough birds. Penguins are very tough birds."

He notes that studies of African penguins cleaned after oil spills show that most survive and go on to breed.

Plus, Fry says, studies done years ago may not reflect the success rates that rescuers could have today because modern rehabilitation techniques cause birds less stress, and birds are carefully monitored to make sure they are ready to be released.

"The responders are getting much better at assessing the health of the birds," Fry says.

Little Data

But some scientists say it's not clear how much difference that makes for the birds' survival.

"They are getting better care in captivity," says Dan Anderson, a biologist at the University of California, Davis, who has studied the effect of oil on birds.

Still, he says, "I'd like to see a report, you know, with statistics and everything on how well these newer techniques are working."

About 20 years ago, he and Fry collaborated on a study that used radio tracking to follow brown pelicans in California that had gotten caught in oil spills, and then cleaned up and released.

"There was one bird that made it for 19 years," Anderson says. "But most of the birds didn't even make it through the first six months."

And the survivors didn't seem to breed, at least during two years of tracking. Anderson says he thinks scientists should try to find out if brown pelicans in this latest spill fare any better.

"The question is still under debate, and legitimately so," he says. "Some follow-up work on this oil spill needs to be done."

Workers who clean oiled birds also want to see more research on how the animals do once they are released.

Mark Russell, a project manager with the International Bird Rescue Research Center, says that the Gulf spill seems like "a golden opportunity to find more information out."

But Russell says that in the absence of clear answers, the birds' suffering still demands action.

"Until we know, we have a moral obligation to stay the course and care for these animals," he says, "and we owe it to each individual animal."

Sometimes, Russell says, euthanasia may be the right choice if it looks like there's no chance a bird could return to the wild. But if recovery seems possible, he thinks a bird should get that chance. Copyright 2010 National Public Radio. To see more, visit http://www.npr.org/.